GM-CSF and interleukin 3 (IL-3) are two of many growth factors that affect the survival, growth and differentiation of hematopoietic cells. The receptors for these factors consist of an a subunit that is responsible for the specificity of ligand binding and a shared subunit known as the common β chain (βc). The significant α subunit homology together with shared β subunit composition of these receptor complexes accounts for the similar activities that IL-3 and GM-CSF have on hematopoietic cells.
The signal transduction pathways of IL-3 and GM-CSF are nearly identical [1]. An early event for both following ligand binding is the tyrosine phosphorylation of βc which is believed to be important in the activation of several signal transduction pathways. Jak2 which is constitutively bound to βc in the absence of growth factor is one of the kinases responsible for the tyrosine phosphorylation of βc [2]. Phosphorylated tyrosine residues on βc allow interactions with proteins containing src homology 2 domains (SH2) such as Shc [3, 4 ], Shp-2 [5], and STAT 5 [6]. Activated Jak2 also phosphorylates bound STAT 5 molecules resulting in homo- or heterodimerization with other STATs and entry into the nucleus where they act as transcriptional regulators of a variety of genes [7]. Shc interactions with βc leads to recruitment of grb2 and sos[8], and activation of Ras [9] and MAP kinase. GM-CSF and IL-3 activation of PI3K [10, 11] also appears to be mediated through βC via interactions with lyn [12, 13], and possibly SHP2 [14]. RACK1 is another molecule which is constitutively bound to βC in the absence of ligand [15]. This protein may regulate the activities of the tyrosine kinases Src and Lck and protein kinase C. However survival and at least a limited degree of proliferation has been shown to occur in cells with a mutant βC that does not contain any tyrosine residues, demonstrating redundancy in the signaling process [16, 17].
Growth factors are essential for the survival, proliferation and differentiation of normal and malignant cells. GM-CSF, along with IL-6, EGF, and IGF-1 are among the growth factors known to be important regulators of carcinoma cells, e.g., prostate carcinoma cells [45] [72][73][74][76][47][63]. For example, the GM-CSF receptor is expressed in prostate carcinoma cell lines and in primary prostate tumor[47][63]. Some prostate carcinomas even produce GM-CSF, which results in autocrine mediated proliferation and growth factor independence [75][77]. Identifying key regulatory proteins and pathways involved in GM-CSF signaling would be useful for the development of new modalities for the detection and treatment of cancer, e.g. prostate cancer.
Cancer of the prostate is the most commonly diagnosed cancer in men and is the second most common cause of cancer death (Carter, et al., 1990; Armbruster, et al., 1993). If detected at an early stage, prostate cancer is potentially curable. However, a majority of cases are diagnosed at later stages when metastasis of the primary tumor has already occurred (Wang, et al., 1982). Early diagnosis is problematic because the current tests tend to provide a substantial number of false positives and many individuals who test positive in these screens do not develop cancer. Present treatment for prostate cancer includes radical prostatectomy, radiation therapy, or hormonal therapy. No systemic therapy has clearly improved survival in cases of hormone refractory disease. With surgical intervention, complete eradication of the tumor is not always achieved and the observed re-occurrence of the cancer (12-68%) is dependent upon the initial clinical tumor stage (Zietman, et al., 1993). Thus, alternative methods of diagnosis, and treatment including prognosis, prophylaxis or prevention woudl desirable.
Mitochondria are cellular organelles with various tasks, including cellular energy production. Therefore, mitochondrial disorders most commonly manifest in tissues highly dependent on biological energy: the brain, heart, muscle and the main sense organs, in particular the eye and inner ear. Mitochondrial diseases include phenotypes resembling several rather common conditions, such as myopathy, hearing impairment, epilepsy, diabetes, muscle weakness or paralysis.
Mitochondrial disorders can be caused by mutations in the genes in mitochondrial DNA (mtDNA) or nuclear DNA. While mtDNA encodes only 37 genes, the number of nuclear DNA genes that encode proteins essential for mitochondrial function is unknown. Identification of these novel nuclear genes would be an important step in diagnostic and prognostic analysis and eventually treatment of mitochondrial diseases associated with defects in the proteins encoded by the nuclear genes.
Alzheimer's Disease (“AD”) is a neurodegenerative illness characterized by memory loss and other cognitive deficits. McKhann et al., Neurology 34: 939 (1984). It is the most common cause of dementia in the United States. AD can strike persons as young as 40-50 years of age, yet, because the presence of the disease is difficult to determine without dangerous brain biopsy, the time of onset is unknown. The prevalence of AD increases with age, with estimates of the affected population reaching as high as 40-50% by ages 85-90. Evans et al., JAMA 262: 2551 (1989); Katzman, Neurology 43: 13 (1993).
By definition, AD is definitively diagnosed through examination of brain tissue, usually at autopsy. Khachaturian, Arch. Neurol. 42: 1097 (1985); McKhann et al., Neurology 34: 939 (1984). Neuropathologically, this disease is characterized by the presence of neuritic plaques (NP), neurofibrillary tangles (NFT), and neuronal loss, along with a variety of other findings. Mann, Mech. Ageing Dev. 31: 213 (1985).
Thus far, diagnosis of AD has been achieved mostly through clinical criteria evaluation, brain biopsies and post mortem tissue studies. Research efforts to develop methods for diagnosing Alzheimer's disease in vivo include (1) genetic testing, (2) immunoassay methods and (3) imaging techniques.